Investments (Net Investment Income - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Income (Loss) from Equity Method Investments	$ 1,000	$ (688)	$ 2,300	$ (365)

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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